Overnight Heart Rate Variability During Sleep Disturbance In Peri- And Postmenopausal Women.

OBJECTIVES: Disturbed sleep, common during the climacteric, is associated with increased sympathetic activity, a cardiovascular risk factor. We evaluated sleep disturbance effect on autonomic nervous function in climacteric women. METHODS: Seventeen perimenopausal and 18 postmenopausal women underwent a sleep study protocol: an adaptation night, a reference night, and a sleep disturbance night, with a hand loosely tied to the bed to allow blood sampling. This procedure was repeated after six months of menopausal hormone therapy (MHT) or placebo. Sleep disturbance and MHT effects on overnight heart rate variability (HRV) were analyzed. RESULTS: At baseline, sleep disturbance increased vagal HRV in postmenopausal women, but no changes were seen in perimenopausal women. At six months, sleep disturbance increased total HRV power in the perimenopausal placebo group, and increased nonlinear vagal HRV in the postmenopausal placebo group, but no other changes were seen. MHT did not have any effects on HRV, neither at perimenopause nor at postmenopause. CONCLUSIONS: External sleep disturbance had only minor effects on HRV across menopause. MHT had no detectable HRV effects.

Child Eveningness as a Predictor of Parental Sleep.

Child eveningness has been associated with many adverse outcomes for children. The aim of this study was to assess whether child eveningness poses a risk to parental sleep quality in follow-up. A total of 146 children (57% adopted, 47% boys, mean age at follow-up 5.1 years [standard deviation 1.7]) completed a 1-week actigraph recording to analyze their sleep twice, 1 year apart. The parents completed the Child ChronoType Questionnaire for their child and a short version of the Morningness-Eveningness Questionnaire for themselves and the Jenkins Sleep Scale for their sleep quality. Linear regression analyses showed that subjective parental sleeping problems at baseline were associated with subjective parental sleeping problems at follow-up. A morning-type child decreased the risk of parental sleeping problems at the 1-year follow-up compared to the child evening chronotype. Additionally, the child intermediate chronotype decreased the risk of maternal sleeping problems at the 1-year follow-up compared to the evening chronotype of the child. Parents of evening-type children experienced more sleeping problems in the follow-up, compared to parents of morning-type children. This finding encourages parents and professionals to steer the diurnal rhythm of evening-type children toward an earlier daily routine.

Changes in objectively measured sleep among internationally adopted children in 1-year follow-up during the first years in new families.

Background: Psychosocial risks and environmental changes experienced by internationally adopted children may predict sleep problems, which are incidentally among the main concerns of adoptive parents. Several questionnaire studies have found sleep of internationally adopted children to be problematic, but none of those used an objective measure in a controlled study. Objective: To determine whether the objectively recorded sleep of internationally adopted children is worse than their controls who are living with their biological parents. Methods: To this case-control part of the Finnish Adoption Study, we recruited children who were adopted internationally to Finland between October 2012 and December 2016. Simultaneously, control children were recruited from 16 daycare centers. To assess sleep in children, actigraphy recordings were made twice, 1 year apart, between December 2013 and April 2018. In the adopted group, the first assessment took place 10 months after they had arrived in their families. The associations between adoption status and sleep parameters were analyzed using linear mixed modeling and adjusted for multiple potential confounders, including child age. Results: Seventy-eight internationally adopted children (boys 64%) aged 1-7 years and 99 controls (boys 53%) aged 2-6 years attended the first sleep recording. The recordings showed that the internationally adopted children slept longer (B = 0.48, 95% CI 0.23-0.73, P < 0.001) than the controls. There were no significant differences in sleep fragmentation or sleep efficiency between the groups. During the 1-year follow-up, the sleep patterns of the adopted children approached those of the controls. Conclusions: The internationally adopted children spent more time in bed and slept more than their control children in both recordings. However, their sleep patterns were not very different from those of their peers and the differences appeared to vanish during the first years in their new family.

Can real-life driving ability be predicted by the Maintenance of Wakefulness Test?

Objective: Drowsy driving is a profound road safety issue. In patients with excessive daytime sleepiness (EDS), the Maintenance of Wakefulness Test (MWT) is commonly used to evaluate driving ability. However, there is little evidence that MWT predicts driving performance, and several sleep latency cutoffs have been suggested. Methods: Based on a retrospective chart analysis of patients with an MWT and a driving ability assessment between January 2006 and November 2014, we identified 63 studies in 60 patients. The driving ability assessment judged the patients as qualified or disqualified for commercial driving. MWT latencies to 3 s of alpha activity, 3 s of drowsiness (microsleep), and sleep onset were compared between qualified and disqualified patients and their validity to identify driving qualification was evaluated. Results: Disqualified patients had shorter alpha, microsleep, and sleep latencies, but the latency distributions were widely overlapping. MWT accuracy to predict driving performance was poor: two thirds of short sleep latencies were false positives. Adding information from alpha and microsleep latencies added little extra accuracy. Conclusions: MWT results correlate poorly with driving performance in a 2-h test irrespective of sleep latency cutoff or added alpha/microsleep latency data. Better diagnostic tools are needed to evaluate driving performance in patients with EDS.

Normative values for sleep parameters in pre-schoolers using actigraphy.

OBJECTIVE: There are currently no reference values for actigraphy-measured sleep length and fragmentation in preschool children. We created standardized parameters using a community sample. METHODS: Ninety-seven 2-to-6-year-old children (56 boys) wore an actigraph on their non-dominant wrist for seven days. The data was extracted and scored, calculating total sleep time, sleep latency, sleep efficiency, fragmentation index, circadian rhythm length, cosine peak and light/dark ratio. Subjects were divided into groups of 2-3-year-olds, 4-5-year-olds and 6-year-olds. Means and standard deviations were calculated, and reference values were created using the 2.5th and the 97.5th percentiles. RESULTS: Reference intervals were 7 h 23 min-9 h 47 min for 24-hour total sleep time, 0.2-48.4 min for sleep latency, 69-87% for sleep efficiency, 23-53% for fragmentation index, 23 h 39 min-24 h 24 min for circadian rhythm length, 12:37-15:53 for the timing of the cosine peak, and 1.14-5.63 for the light-dark ratio. With increasing age, daily sleep time, sleep latency, sleep fragmentation, and napping decreased. CONCLUSIONS: We were able to create previously non-established reference values, including trends with increasing age, on actigraphy-assessed sleep in preschool children. SIGNIFICANCE: Sleep disorders in young children are easier to evaluate against normative data.

First-Night Effect on Sleep in Different Female Reproductive States.

OBJECTIVES: In sleep laboratory studies, the new environment is generally considered to disturb sleep during the first night. However, older women have rarely been studied. Although menopause and hormone therapy affect sleep, their impact on the first-night effect is virtually unknown. PARTICIPANTS: Four groups of women with no sleep laboratory experience: young on hormonal contraceptives (n = 11, 23.1 [0.5] years), perimenopausal (n = 15, 48.0 [0.4] years), postmenopausal without hormone therapy (HT; off-HT, n = 22, 63.4 [0.8] years) and postmenopausal with HT (n = 16, 63.1 [0.9] years). PROCEDURE: A cross-sectional study. METHODS: Polysomnography was performed over two consecutive nights and the first-night effect and group differences were evaluated. Questionnaire-based insomnia and sleepiness scores were correlated to sleep variables and their between-night changes. RESULTS: Although sleep in young women was deeper and less fragmented than in the other groups, first-night effect was similar in all study groups. Total sleep time, sleep efficiency, and S1 and S2 sleep increased, and wake after sleep onset, awakenings per hour of sleep, S2 and REM latencies, and percentage of SWS decreased from the first to the second night. Perimenopausal women had more insomnia complaints than other women. Insomnia complaints were associated with more disturbed sleep but not with the first-night effect. CONCLUSIONS: A first night in a sleep laboratory elicits a marked interference of sleep architecture in women of all ages, with a carryover effect of lighter sleep on the second study night. Menopausal state, HT use, or insomnia complaints do not modify this effect.

First-night effect on cardiac autonomic function in different female reproductive states.

Decreases in heart rate variability, a marker of autonomic nervous system function, are associated with increased cardiovascular mortality. Heart rate variability increases in non-rapid eye movement sleep, peaking in slow-wave sleep. Therefore, decreasing the amount of deep sleep, for example, by introducing patients to a sleep laboratory environment, could decrease heart rate variability, increasing cardiovascular risk. We studied four groups of women with no previous sleep laboratory experience: young [n = 11, 23.1 (0.5) years]; perimenopausal [n = 15, 48.0 (0.4) years]; postmenopausal without hormone therapy [n = 22, 63.4 (0.8) years]; and postmenopausal on hormone therapy [n = 16, 63.1 (0.9) years], using a cross-sectional design. Polysomnography including electrocardiogram was performed over two consecutive nights. Heart rate variability was assessed overnight, and the first-night effect on heart rate variability was analysed. Furthermore, correlations between heart rate variability and sleep variables were analysed. Using combined groups, only minor changes were observed in non-linear heart rate variability, indicating increased parasympathetic tone from the first to the second night. No group differences in first-night effect were seen. Heart rate variability and sleep variables were not significantly correlated. Heart rate variability decreased with increasing age, and it was lowest in the postmenopausal women on hormone therapy. We conclude that a first night in a sleep laboratory elicits only minimal changes in overnight vagally mediated non-linear heart rate variability in women irrespective of reproductive state. This finding warrants further analyses in different sleep stages, but suggests that changes in sleep architecture per se do not predict the autonomic strain of a poor night.

Poor Parental Sleep and the Reported Sleep Quality of Their Children.

BACKGROUND: Pediatric sleep disturbances are regularly diagnosed on the basis of parental reports. However, the impact of parental sleeping problems on parental perceptions and reports of their child's sleep has not yet been studied. We hypothesized that poor parental sleep decreases the parent-reported child sleep quality. METHODS: A 1-week actigraph recording was performed in 100 children aged 2 to 6 years recruited in 16 day care centers. Their biological parents completed a sleep diary and a Sleep Disturbance Scale for Children (SDSC) on children's sleep. The parents also completed the Jenkins' sleep scale on their own sleep, the 12-item General Health Questionnaire, and questions on demographic factors. Linear regression analyses were performed to study the association of the parental Jenkins' score on their child's total SDSC score. Analyses were also performed for 3 of the subscales of the SDSC: disorders of excessive somnolence, disorders of initiating and maintaining sleep, and sleep-wake transition disorders. RESULTS: Parental sleeping problems were associated with more frequent reporting of children's sleeping problems. This association was unexplained by the actigraph measures of children's sleep, such as actual 24-hour sleep time and sleep efficiency, parental mental health problems, or any other tested potential confounder or mediator. Similar correlations were seen for the 3 analyzed subscales. CONCLUSIONS: Parental sleep quality was associated with overreporting of sleep problems in their children. This finding emphasizes the importance of considering parental sleep quality in the diagnosis, treatment, and research of pediatric sleeping problems.

Evaluation of patients' sleep by nurses in an ICU.

AIMS AND OBJECTIVES: To determine how intensive care unit evaluations of patients' sleep by nurses correspond to polysomnography and if changes in patients' physiologic parameters could be helpful in sleep evaluation. BACKGROUND: The evaluations of patients' sleep by nurses have not corresponded very well with objective sleep recordings, so there is a need for further knowledge in this field. DESIGN: Correlational study of patients' sleep, nurses' sleep evaluations and the sleep-related heart rate and blood pressure changes. METHODS: The standard overnight polysomnography was recorded on 21 patients. Simultaneously, nurses marked into an electronic patient care documentation system all the changes noted in the patients' sleep status. Patients' arterial blood pressure and heart-rate data were automatically saved into the electronic patient care documentation. RESULTS: The evaluations of patients' sleep/wake state by nurses corresponded to polysomnography 68% of the time. A correlation was found between nurses' evaluations and polysomnography recordings only on total sleep time. There was no correlation in the other sleep aspects (sleep latency, amount of awakenings or movements during sleep). Most patients' blood pressures and heart rate varied according to sleep/wake state. There was less variation if the patient had received noradrenalin for blood pressure control. CONCLUSION: The evaluations of patients' sleep/wake state by nurses only correspond to the polysomnography two-thirds of the time. Thus, more sophisticated evaluation methods should be developed to aid nurses in sleep evaluations. Sleep-related changes in blood pressure and heart rate can be seen in intensive care unit patients, so using these parameters as part of the patients' sleep evaluation should be further explored. RELEVANCE TO CLINICAL PRACTICE: The nurses' evaluation practices of intensive care unit patients' sleep need further development. Monitoring the changes in patients' heart rate and blood pressure may aid in evaluating his/her sleep.

Obstructive sleep apnea in psychiatric outpatients. A clinic-based study.

Psychiatric diseases and symptoms are common among patients with obstructive sleep apnea (OSA). However, only a few studies have examined OSA in psychiatric patients. At the outpatient clinic of the Uusikaupunki Psychiatric Hospital, Finland, we used a low referral threshold to a diagnostic sleep study. An ambulatory cardiorespiratory polygraphy was performed in 114 of 221 patients. 95 patients were referred by the psychiatric clinic and 19 were examined in other clinical settings. We reviewed the medical files and retrospectively assessed the prevalence of OSA and the effect of gender, age, obesity, hypertension, type 2 diabetes, alcohol abuse, and symptoms suggesting OSA. 58 of the 221 patients (26.2%), 30 of 85 men (35.3%) and 28 of 136 women (20.6%), had OSA as determined by an apnea-hypopnea index (AHI) of 5/h or more. 20 patients (12 men and 8 women) had moderate or severe OSA (AHI ≥ 15/h). 46 patients (including 11 patients with moderate or severe OSA) were identified in the psychiatric clinic. In univariate analysis, a high body mass index, male gender, hypertension, snoring, and a history of witnessed apneas during sleep were associated with the presence of OSA. In multivariate analysis, a history of witnessed apneas did not remain significant. Age, type 2 diabetes, alcohol abuse, excessive daytime sleepiness (EDS), and fatigue did not associate with the presence of OSA. Our findings suggest that in psychiatric outpatients OSA is common but underdiagnosed. Presentation is often atypical, since many patients with OSA do not report witnessed apneas or EDS.

Sleep and nursing care activities in an intensive care unit.

This study aimed to describe the quality of sleep of non-intubated patients and the night-time nursing care activities in an intensive care unit. The study also aimed to evaluate the effect of nursing care activities on the quality of sleep. An overnight polysomnography was performed in 21 alert, non-intubated, non-sedated adult patients, and all nursing care activities that involved touching the patient were documented by the bedside nurse. The median (interquartile range) amount of sleep was 387 (170, 486) minutes. The portion of deep non-rapid-eye-movement (non-REM) sleep varied from 0% to 42% and REM sleep from 0% to 65%. The frequency of arousals and awakenings varied from two to 73 per hour. The median amount of nursing care activities was 0.6/h. Every tenth activity presumably awakened the patient. Patients who had more care activities had more light N1 sleep, less light N2 sleep, and less deep sleep. Nursing care was often performed while patients were awake. However, only 31% of the intervals between nursing care activities were over 90 min. More attention should be paid to better clustering of care activities.

Cardiac autonomic changes after 40 hours of total sleep deprivation in women.

OBJECTIVES: The effect of total sleep deprivation on heart rate variability (HRV) in groups of postmenopausal women on oral hormone therapy (HT) (on-HT, n = 10, 64.2 (1.4) years), postmenopausal women without HT (off-HT, n = 10, 64.6 (1.4) years) and young women (n = 11, 23.1 (0.5) years) was studied using a prospective case-control setup. METHODS: Polysomnography was performed over an adaptation night, a baseline night, and a recovery night after 40 h of total sleep deprivation. Time and frequency domain and nonlinear HRV from overnight electrocardiogram recordings were compared between groups during baseline and recovery nights. Further, the changes in HRV from baseline to recovery were analysed and compared between groups. Finally, correlations of HRV to percentages of sleep stages and measures of sleep fragmentation were analysed during baseline and recovery. RESULTS: Young women had higher HRV than older women; the most marked difference was between young and on-HT postmenopausal women. Sleep deprivation induced a decrease in frequency domain HRV in young and in off-HT women, an increase in α2 in off-HT women, and an increase in mean heart rate in on-HT women. The sleep deprivation effect was mainly uncorrelated to changes in sleep parameters. CONCLUSIONS: Acute total sleep deprivation has a deleterious effect on the autonomic nervous system in young women, but an even more pronounced effect in postmenopausal women. Hormone therapy use in late postmenopause does not give protection against these changes. These harmful effects may partly explain the increased cardiovascular morbidity and overall mortality associated with sleep loss.

Evaluating adult patients' sleep: an integrative literature review in critical care.

BACKGROUND: Patients in a critical care unit sleep quite poorly even when they appear to be sleeping. Sleep is light and fragmented. Acute lack of sleep causes patients suffering in the form of fatigue, irritability, disorientation and hallucinations. It may also affect their recovery and immune defence. To promote sleep, nurses must be able to evaluate patients' sleep reliably. AIM AND OBJECTIVES: Our aim was to form a comprehensive overview of the sleep evaluation methods in critical care. Our objectives were to determine the content and the quality of the methods as reported by the researchers. This overview hopefully improves the use of the sleep evaluation methods as part of sleep promoting nursing interventions and practices. METHOD: The literature search was performed from the Ovid MEDLINE, CINAHL, an 'All EBM Reviews', and PsycINFO databases. The search terms sleep, evaluating sleep and critical care were used. An integrative review method was used to analyse the data. RESULTS: According to the 52 articles of this review, there is a wide variety of methods to evaluate patients' sleep in critical care by observation, by asking for patient's own perception and by objective measures. Most instruments evaluate only total sleep time or the quality of sleep in general. The validity and reliability of the instruments has been insufficiently reported. Some questionnaires for patients' perception have been tested and used in several studies. CONCLUSION: Sleep evaluation instruments do not cover all dimensions of sleep since they mostly measure total sleep time or estimate the overall quality of sleep. The quality of the sleep evaluation instruments varies from scientifically tested tools to untested instruments. This review will allow nurses to recognise the strengths and limitations of sleep evaluation instruments when selecting one to be used in critical care. Valid information about patients' sleep enables nurses to facilitate it.

[Paroxysmal feeling of suffocation during sleep--a diagnostic challenge]. / Unenaikainen kohtauksellinen tukehtumisen tunne--diagnostinen haaste.

Our patient suffered from nocturnal awakenings due to paroxysmal feelings of suffocation for three years. He was extensively examined at the community health centre and at the departments of neurology, psychiatry, oral diseases and respiratory medicine of the district hospital and the university hospital. The clinical hunch of the night nurses of the department of respiratory medicine and video EEG monitoring recommended by the sleep disorders team eventually revealed the real cause of the patient's symptoms.

Postmenopausal estrogen therapy modulates nocturnal nonlinear heart rate dynamics.

OBJECTIVE: To study the effects of postmenopausal estrogen therapy (ET) on nocturnal nonlinear heart rate variability (HRV). DESIGN: In this prospective, randomized, double-blind, placebo-controlled study, 71 healthy hysterectomized postmenopausal women received either transdermal estradiol or placebo for 3 months. After a washout period of 1 month, the treatments were reversed. Sleep studies were performed after both treatment periods. One steady-state epoch per night of the awake state, stage 2 (light) non-rapid eye movement (REM) sleep, stage 3-4 (deep) non-REM sleep, also known as slow-wave sleep, and REM sleep was extracted. From the electrocardiogram, nonlinear HRV was analyzed as the fractal scaling exponents alpha1 and alpha2, approximate entropy (ApEn), and the Poincaré plot variability coefficients SD1 and SD2. These were correlated to ET use in both different sleep stages and averaged across all sleep stages. RESULTS: During ET, the nocturnal ApEn decreased from 0.80 +/- 0.01 to 0.74 +/- 0.02 (P < 0.05), the most marked reduction occurring during slow-wave sleep (from 0.77 +/- 0.05 to 0.63 +/- 0.06, P < 0.05). In addition, SD2 decreased in slow-wave sleep and REM sleep during ET (P < 0.05 for both). In light non-REM sleep, alpha1 slightly increased during ET (P < 0.05). CONCLUSIONS: ET has a slightly but distinctively attenuating effect on some nocturnal nonlinear measures of HRV, especially on complexity of heart rate dynamics. This implies that ET may have potentially deleterious effects on cardiovascular health during sleep.

Sleep stage dependent patterns of nonlinear heart rate dynamics in postmenopausal women.

OBJECTIVE: To study the effects of sleep stage changes on nocturnal nonlinear heart rate variability (HRV) in postmenopausal women. DESIGN: A prospective study. POPULATION: Seventy-one healthy postmenopausal women. METHODS: The women underwent two separate sleep studies four months apart. One steady state epoch per night of the awake state, stage 2 (light) non-REM sleep, stage 3-4 (deep) non-REM sleep and REM sleep were extracted. From the ECG, the fractal scaling exponents alpha(1) and alpha(2), approximate entropy (ApEn), the Poincaré plot variability coefficients SD1 and SD2, along with the low (LF) and high frequency (HF) bands of linear HRV as well as the LF/HF ratio were calculated. RESULTS: None of the spectral measures of HRV changed significantly during the non-REM sleep compared to awake state. However, in non-REM sleep, alpha(2) (p<0.001) decreased significantly compared to the awake state, while alpha(1) and ApEn remained unchanged. SD1 was slightly increased in stage 2 sleep (p<0.05), while SD2 decreased in slow wave sleep (p<0.001). In REM sleep, alpha(2) values returned to the awake values, while ApEn and alpha(1) increased above the awake levels (p<0.01 for all variables), and SD1 decreased (p<0.01). HF spectral component decreased slightly (p<0.05 compared to stage 2 sleep) and LF/HF ratio increased during REM sleep (p<0.001). ApEn and alpha(2) had no correlations with any of the spectral measures of HRV, and alpha(1) had a modest correlation with the LF/HF ratio only during sleep. CONCLUSIONS: We found that nonlinear indices of HRV describe specific features in HR dynamics during various sleep stages that are not detected by traditional spectral HRV indices.

Impact of menopause on the manifestation and severity of sleep-disordered breathing.

BACKGROUND: Decreased production of female hormones might explain the increased prevalence of sleep-disordered breathing in postmenopausal women. OBJECTIVES: We evaluated, whether menopause has an impact on the manifestation of sleep-disordered breathing in terms of signs, symptoms, and breathing pattern. METHODS: The study was a cross-sectional study utilizing a patient database, hospital records, sleep studies, and questionnaires. The hospital records and sleep studies were reviewed in 601 consecutive women studied between 1994 and 1998 in a university hospital pulmonary clinic. The records were completed with questionnaires. RESULTS: Nocturnal breathing abnormalities covered a greater proportion of the night in postmenopausal than in premenopausal women (68.1% versus 35.8% of time in bed, p<0.0001), and the prevalence of sleep-disordered breathing tended to be higher (86.2% versus 79.4% of time in bed, p=0.057). The body mass indices and the major symptoms of sleep-disordered breathing were similar in pre- and postmenopausal women. Postmenopausal women had less nasal congestion (p<0.001) than premenopausal ones. Body mass index was a significant explanatory factor of daytime sleepiness. CONCLUSIONS: Post- and premenopausal women present with similar signs and symptoms when referred to sleep studies. However, sleep-disordered breathing is more severe in postmenopausal than in premenopausal women.

Menopausal estrogen therapy predicts better nocturnal oxyhemoglobin saturation.

OBJECTIVES: The respiratory responses in the few previous studies evaluating the effects of short-term unopposed estrogen therapy on breathing in postmenopausal women have been inconsistent. We performed a study to investigate whether long-term estrogen therapy would prevent age-related decline in nocturnal arterial oxyhemoglobin saturation and whether higher serum estradiol concentration is associated with better arterial oxyhemoglobin saturation. METHODS: Sixty-four healthy postmenopausal women were followed-up for 5 years in a 5-year prospective open follow-up study. The women were users or non-users of estrogen therapy according to their personal preference. RESULTS: Mean overnight arterial oxyhemoglobin saturation was similar at baseline (94.3 +/- 1.1%) and after follow-up (94.5 +/- 1.6%). Present estrogen users had higher mean arterial oxyhemoglobin saturation (95.2 +/- 1.4%) than present non-users (94.0 +/- 1.5%), when adjusted for age and body mass index (p = 0.042). The change in mean arterial oxyhemoglobin saturation during follow-up was not associated with serum estradiol concentration at baseline but associated with estradiol at follow-up (p = 0.042), when adjusted for age and body mass index. At follow-up, women with higher serum estradiol concentration had also higher mean nocturnal arterial oxyhemoglobin saturation (Pearson r = 0.29, p = 0.019) and lower apnea-hypopnea index (Spearman r = -0.28, p = 0.031). The pooled current estrogen users spent proportionally less time with SaO(2) below 90% than non-users (ANCOVA adjusted for age and BMI, p = 0.017). CONCLUSIONS: Estrogen use and especially high serum estradiol concentration predict higher mean overnight arterial oxyhemoglobin saturation. The present data suggest that estrogen therapy has favorable respiratory effects.